Exchanger assembly for respiratory treatment

ABSTRACT

An exchanger conduit permits temperature and/or humidity conditioning of a gas for a patient respiratory interface. In an example embodiment, a conduit has a first channel and a second channel where the first channel is configured to conduct an inspiratory gas and the second channel configured to conduct an expiratory gas. An exchanger is positioned along the first channel and the second channel to separate the first channel and the second channel. The exchanger is configured to transfer a component (e.g., temperature or humidity) of the gas of the second channel to the gas of the first channel. In some embodiments, an optional flow resistor may be implemented to permit venting at pressures above atmospheric pressure so as to allow pressure stenting of a patient respiratory system without a substantial direct flow from a flow generator of respiratory treatment apparatus to the patient during patient expiration.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. § 371of International Application No. PCT/AU2012/001382 filed Nov. 9, 2012,published in English, which claims the benefit of the filing date ofU.S. Provisional Patent Application No. 61/558,648 filed Nov. 11, 2011,the disclosure of which is hereby incorporated herein by reference.

FIELD OF THE TECHNOLOGY

The present technology relates to conduits for a respiratory treatmentsuch as a conduit having a heat and/or humidity exchanger for a maskassembly that may be implemented for a respiratory pressure treatmentincluding, for example, Non-invasive Positive Pressure Ventilation(NPPV) and continuous positive airway pressure (CPAP) therapy of sleepdisordered breathing (SDB) conditions such as obstructive sleep apnea(OSA).

BACKGROUND OF THE TECHNOLOGY

Treatment of sleep disordered breathing (SDB), such as obstructive sleepapnea (OSA), by a respiratory treatment apparatus such as a continuouspositive airway pressure (CPAP) flow generator system involves adelivery of air (or other breathable gas) at pressures above atmosphericpressure to the airways of a patient via a conduit and/or a mask.Typically, the mask fits over the mouth and/or nose of the patient, ormay be an under-nose style mask such as a nasal pillows or nasal cushionstyle mask. Pressurized air flows to the mask and to the airways of thepatient via the nose and/or mouth. A washout vent in the mask or conduitmay be implemented to discharge the exhaled gas from the mask toatmosphere.

Respiratory treatment apparatus may include a flow generator, an airfilter, an air delivery, conduit connecting the flow generator to themask, various sensors and a microprocessor-based controller. The flowgenerator may include a servo-controlled motor and an impeller. The flowgenerator may also include a valve capable of discharging air toatmosphere as a means for altering the pressure delivered to the patientas an alternative to motor speed control. The sensors may measure,amongst other things, motor speed, gas volumetric flow rate and outletpressure, such as with a pressure transducer, flow sensor or the like.The controller may also include data storage capacity with or withoutintegrated data retrieval/transfer and display functions. Positiveairway pressure may be delivered in many forms.

As previously mentioned, a CPAP treatment may maintain a treatmentpressure across the inspiratory and expiratory levels of the patient'sbreathing cycle at an approximately constant level. Alternatively,pressure levels may be adjusted to change synchronously with thepatient's breathing cycle. For example, pressure may be set at one levelduring inspiration and another lower level during expiration for patientcomfort. Such a pressure treatment system may be referred to asbi-level. Alternatively, the pressure levels may be continuouslyadjusted to smoothly replicate changes in the patient's breathing cycle.A pressure setting during expiration lower than inspiration maygenerally be referred to as expiratory pressure relief. As described bySullivan in U.S. Pat. No. 4,944,310, positive airway pressure treatmentstypically provide gas under pressures to the patient in the range of 4to 15 cmH₂O from the device and may involve flow rates of at about 120liters/minute. Some of the air may escape via an end restriction or ventand not be delivered to the patient. These pressure settings may also beadjusted based on the detection of conditions of the patient's airway orrespiration. For example, treatment pressure may be increased in thedetection of partial obstruction, apnea or snoring. In some cases,positive airway pressure may be adapted to provide ventilation support.For example, a patient's ventilatory needs may be supported on abreath-by-breath basis by automatically calculating a target ventilationand adjusting the pressure support generated by an apparatus, such as abi-level pressure treatment apparatus, so as to achieve the targetventilation.

Respiratory treatment apparatus are sometimes provided with accessorycomponents for comfort conditioning of the flow or pressurized airsupplied by the flow generator. For example, the supplied air may beapplied to a humidifier to humidify and warm the treatment gas prior toits delivery to a patient. Similarly, various heating elements can beconnected with a delivery conduit to help in maintaining a particulartemperature of the supplied gas as it is conducted to the patient from asupply unit or humidifier.

There may be a desire to improve efficiency of heating and/orhumidification and/or pressurised delivery of a breathable gas forrespiratory treatments.

SUMMARY OF THE TECHNOLOGY

One aspect of the present technology relates to an exchanger configuredto exchange a component of an inspiratory gas with a component of anexpiratory gas.

Another aspect of the technology relates to a conduit configured with aheat and/or humidity exchanger.

A still further aspect of the technology relates to a conduit with anexpiratory flow resistor.

Further aspects of the present technology relate to a respiratorytreatment apparatus configured to deliver a respiratory treatment withsuch a conduit, expiratory flow resistor and/or exchanger.

Some such embodiments of the present technology involve conduitsconfigured for dynamic expiratory venting.

Some embodiments of the present technology include an exchanger conduitto condition a breathable gas for a patient interface that delivers arespiratory treatment. The exchanger conduit may include a conduithaving a first channel and a second channel. The first channel may beconfigured to conduct an inspiratory gas and the second channel may beconfigured to conduct an expiratory gas. The exchanger may be configuredalong the first channel and the second channel to separate the firstchannel and the second channel. The exchanger may also be configured totransfer a component of the gas of the second channel to the gas of thefirst channel.

In some such cases, the exchanger may include a temperature conductingmaterial whereby the component of the gas transferred from the gas ofthe first channel to the gas of the second channel is temperature. Insome such cases, the exchanger may include a moisture conductingmaterial whereby the component of the gas transferred from the gas ofthe first channel to the gas of the second channel is moisture. In somesuch cases, the exchanger may include a hydrophilic material, a carbondioxide rejecting material and/or a cellulose material. In someembodiments, the exchanger may include a folded surface that divides thefirst channel and the second channel. In some cases, the first channeland the second channel each include a plurality of flow pathways suchthat the exchanger divides the pathways with a plurality of generallyparallel wall surfaces. Each such wall surface may separate a pathway ofthe first channel and a pathway of the second channel.

In some such embodiments, the exchanger may include a plurality of heatconducting fins. The exchanger may also include a plurality of capillaryapertures. In some cases, the first channel may include an input end andan output end. The output end may be adapted for interfacing with apatient respiratory system. Optionally, in some such cases, theexchanger conduit may also include a valve. The valve may be configuredat the first channel to permit gas flow through the first channel fromthe input end to the output end but not from the output end to the inputend. In some cases, the output end may include a respiratory mask and/ora coupler for a respiratory mask.

In some such embodiments, the input end may include a coupler for anoutput conduit of a respiratory treatment apparatus. Optionally, thesecond channel may include an input end and an output end. The input endmay be adapted for interfacing with a patient respiratory system and theoutput end may be adapted for interfacing with an expiratory vent toatmosphere. The second channel may include a valve to permit expiratorygas to vent to atmosphere through the expiratory vent and prevent a flowof air into the second channel from atmosphere through the vent. In somecases, the expiratory vent may include a flexible barrier. The flexiblebarrier may be preloaded with a tension to be operable to selectivelyopen the vent to maintain pressure in the second channel below apressure threshold that is greater than atmospheric pressure. In somesuch cases, the expiratory vent may include a pair of tensioning bars,through which the flexible barrier is tensioned.

In some cases of the exchanger conduit, the first channel may alsoinclude an input aperture with a coupler for an oxygen source.Optionally, in some cases, the exchanger may also include first andsecond sets of fins coupled together for temperature exchange. The firstset of fins may extend within the first channel and the second set offins may extend within the second channel. The first and second set offins may be connected by a transverse portion having a capillary surfaceextending longitudinally along the first and second channels between thefirst and second sets of fins.

In some embodiments of the exchanger conduit, a fluid supply aperturemay be included. The fluid supply aperture may include a fluid channelto supply a fluid to a material of the exchanger. In some embodiments, aconduit to the first channel may include a flexible chamber configuredto prevent flow of an expiratory gas in the first channel. Optionally, aconduit to the second channel may include a flexible chamber configuredto prevent flow of an inspiratory gas in the second channel.

In some embodiments, the exchanger may include a flexible divider. Theflexible divider may have a fixed end. The flexible divider may alsohave a lip end. In some cases, the exchanger conduit may include aventing portion. The flexible divider may be configured to move toselectively block and open an aperture of the venting portion of theconduit. The venting portion may include a set of oblique apertures. Theconduit may also include a ribbed divider support. The conduit may alsoinclude a divider seat configured for sealing with a peripheral edge ofthe divider.

In some embodiments, the exchanger may include an adjustment mechanismto selectively increase or decrease an efficiency of the transfer of thecomponent of the gas of the second channel to the gas of the firstchannel. The adjustment mechanism may be configured to increase and/ordecrease a flow contact surface area of the exchanger. In some cases, aprocessor and a sensor may be included. The processor may be configuredto control the adjustment mechanism to adjust the efficiency of theexchanger in response to a signal from the sensor. The sensor may betemperature sensor or a humidity sensor.

Some embodiments of the present technology involve an expiratory flowresistor to permit a stenting pressure above atmospheric pressure in arespiratory conduit. The flow resistor may include a respiratory conduithaving an expiratory flow channel. It may further include an aperture ofthe conduit to release a flow of the expiratory flow channel toatmosphere. It may also include a cover component. The cover componentmay be configured to selectively block the aperture and the covercomponent may be loaded with a tension to block the aperture unless apressure of the expiratory flow channel exceeds a pressure thresholdthat is above atmospheric pressure.

In some such cases of the expiratory flow resistor, the cover componentmay be coupled to a spring and pivot, whereby the spring provides thetension to the cover component. Optionally, the cover component may beflexible and a wall abutment of the conduit may ply the flexible coveragainst the aperture to provide the tension to the cover component. Insome cases, the cover component may include a balloon membrane whereinthe conduit further include a pressurization chamber coupled to a flowgenerator to pressurize the membrane to expand to close the aperture.

In some cases of the expiratory flow resistor, the cover component mayinclude a flexible membrane. Optionally, pressure of the expiratorychannel may expand the membrane to open the aperture. In someembodiments, the cover member may include a flexible membrane, and theconduit may further include a set of bars through which the membrane isinserted to provide the tension to the membrane.

In some embodiments of the expiratory flow resistor, the conduit mayinclude a holder ridge and the cover component may be further configuredwith the holder ridge to prevent flow into the expiratory channel unlessa pressure condition in the expiratory channel falls below atmosphericpressure. In some cases, the cover member may also include a flexiblemembrane and a plug. The plug may be configured to selectively enter theaperture to block the aperture.

In some embodiments of the expiratory flow resistor, the conduit mayalso include an inspiratory channel that may be separated by theexpiratory channel by the cover component. In some such cases, theinspiratory channel may be adapted to be coupled with an output of aflow generator of a respiratory treatment apparatus and an input of apatient interface. In some cases, the inspiratory flow channel mayinclude a one-way valve to permit a flow generator to hold pressure inthe inspiratory flow channel against the cover component withoutdelivering flow to a patient interface through the inspiratory flowchannel during patient expiration.

Some embodiments of the present technology may involve a conduit for abreathable gas for a patient interface that delivers a respiratorytreatment. The conduit may have a first channel and a second channel.The first channel may be configured to conduct an inspiratory gas andthe second channel may be configured to conduct an expiratory gas. Theconduit may also include a flexible channel divider along the firstchannel and the second channel to dynamically create the first channeland the second channel in response to an inspiratory flow and anexpiratory flow or a component of pressure resulting from an inspiratoryflow or an expiratory flow such as a change in static pressure resultingfrom a change in lung volume or a dynamic pressure resulting from aninspiratory or expiratory flow velocity.

In some such cases, the flexible channel divider may include anexchanger to transfer a component of a gas of the first channel to thesecond channel. The component may be temperature and/or humidity.Optionally, the flexible divider may have a fixed end. The flexibledivider may also have a lip end. In some cases, the conduit may includea venting portion such that the flexible divider is configured to moveto selectively block and open an aperture of the venting portion of theconduit. The venting portion may include a set of oblique apertures, aribbed divider support, and/or a divider seat configured for sealingwith a peripheral edge of the divider. Optionally, in some cases, theconduit may also include a continuous vent aperture.

In some cases, the venting portion may include a set of aperturesconfigured at an acute angle with respect to an expiratory flow path ofthe second channel. Optionally, the conduit may also include a conduitbend, and the flexible channel divider may extend across the conduitbend. In some cases, a length of the flexible channel divider may be alength greater than one and one quarter times a width of the conduit.The flexible divider may be configured in the conduit to provide theflexible divider with an expiratory activation side and a gas supplyactivation side, wherein the expiratory activation side has a surfacearea exceeding a surface area of the gas supply activation side. Theflexible divider may also include a lift at a lip end of the divider andthe lift may extend into a channel of the conduit. Optionally, theflexible divider may have a non-planar surface, such as a convex surfaceor a concave surface. The flexible divider may also include one or moreprotuberants configured to seal at least a part of the venting portion.Optionally, the conduit may include a secondary vent and a vent cover,and the flexible divider may be linked to the vent cover for selectivelysealing the secondary vent. In some cases, the flexible channel dividerof the conduit may include a duckbill opening. The duckbill opening maybe configured to selectively block and unblock peripheral apertures of aventing portion of the conduit. In some cases, the conduit may alsoinclude a discrete venting chamber, and the flexible channel divider mayhave a pivot portion within the venting chamber. Such a flexible channeldivider may selectively open the venting chamber to one of a ventingportion for release of expiratory gas and a pressure release portion forequalizing gas of a gas supply with atmosphere.

In some cases, the conduit may include a bypass channel configured topermit a sensing of a gas characteristic to bypass the flexible channeldivider. Optionally, the conduit may be coupled in gas communicationwith a sensor. The sensor may be configured to sense a gascharacteristic attributable to the bypass channel. The sensor may becoupled with a processor. The processor may be configured to estimate agas characteristic of an opposing side of the flexible channel dividerfrom the sensed characteristic. The estimated characteristic may bepatient expiratory flow and/or therapy pressure at a patient interface.

In some cases, the conduit may include an exchanger in series with theflexible channel divider. The conduit may also include a heat moistureexchange material in a bi-directional flow channel in series with theflexible channel divider. Optionally, the conduit may further include aset of divider supports extending from a conduit surface and positionedto support the divider during an inspiratory flow. In some cases, theconduit may further include a set of divider supports extending from aconduit surface and positioned to support the divider during anexpiratory flow. The set of divider supports may be formed by parallelribs longitudinally arranged along the flow path of the conduit.

In some cases, the flexible channel divider may be configured to createan inspiratory channel between a first side of the conduit and a firstside of the divider and an expiratory channel between the opposing sideof the conduit and the opposing side of the divider when the dividertraverses between the opposing sides of the conduit.

Other aspects, features, and advantages of this technology will beapparent from the following detailed description when taken inconjunction with the accompanying drawings, which are a part of thisdisclosure and which illustrate, by way of example, principles of thetechnology. Yet further aspects of the technology will be apparent fromthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further example embodiments of the technology will now be described withreference to the accompanying drawings, in which:

FIG. 1 is a diagram of a conduit apparatus with an exchanger of thepresent technology;

FIG. 2 is a diagram of another embodiment of the conduit apparatus ofFIG. 1;

FIG. 3 is a diagram of an embodiment of the conduit apparatus having anexchanger of the present technology that is suitable for implementationwith a respiratory treatment apparatus;

FIG. 4 is a diagram of another exchanger embodiment suitable for usewith a respiratory treatment apparatus;

FIG. 5 is a diagram of an alternative embodiment of the embodiment ofFIG. 4 with a Starling resistor;

FIGS. 5A and 5B illustrate operation of a Starling resistor in a conduitthat is implemented as a one-way valve shown in both open and closedconfigurations respectively;

FIG. 6 is a diagram of an example heat and humidity exchanger suitablefor use in some embodiments of the present technology;

FIG. 7 is an illustration of a capillary humidity exchanger that may beimplemented in some embodiments;

FIG. 8 is an illustration of an exchanger having conduction fins and acapillary medium for humidity transfer that may be implemented in someembodiments;

FIG. 9 is an illustration of an exchanger having multiple heatconduction channels for inspiratory and expiratory flow and a capillarymedium for humidity transfer that may be implemented in someembodiments;

FIGS. 10A and 10B are cross sectional views of an example conduit andfolded exchanger configuration with inspiratory and expiratory channelsin an example embodiment of the present technology;

FIG. 11 is a cross sectional view of a further conduit and exchangerwith inspiratory and expiratory channels in some embodiments of thepresent technology;

FIG. 12 is a cross sectional view of the conduit and exchanger of FIG.11 including temperature conducting fins;

FIG. 12A is a cross sectional view of the conduit and exchangerincluding a pleated channel;

FIG. 13 illustrates a helical exchanger conduit embodiment of thetechnology;

FIG. 14 shows a still further exchanger conduit embodiment havingmultiple flow paths;

FIGS. 15 and 16 illustrate an example expiratory vent resistor that maybe implemented in some conduit embodiments of the present technology;

FIGS. 17 and 18 illustrate a further flexible expiratory flow resistorthat may be implemented in some conduit embodiments of the presenttechnology;

FIGS. 19 and 20 illustrate a further flexible expiratory flow resistorthat may be implemented in some conduit embodiments of the presenttechnology;

FIG. 21 illustrate a still further flexible expiratory flow resistorwith tensioning posts that may be implemented in some conduitembodiments of the present technology;

FIG. 22 illustrates an example conduit housing for the expiratory flowresistor illustrated in FIG. 21;

FIGS. 23 and 24 illustrate operation of another flexible expiratory flowresistor that may be implemented in some conduit embodiments of thepresent technology;

FIGS. 25A and 25B illustrate operation of another flexible expiratoryflow resistor that may be implemented in some conduit embodiments of thepresent technology;

FIG. 26 is a cross-sectional view of a conduit having a flexible channeldivider that may be configured as an exchanger in some embodiments ofthe present technology illustrated in a position when there is no flowgenerator pressure such that it may serve as an anti-asphyxia device;

FIG. 27 is a cross-sectional view of a further example embodiment of theconduit of FIG. 26 including an oblique venting portions and ribbeddivider support;

FIGS. 28, 29 and 30 illustrate operation of the embodiment of FIG. 27during inspiration, start of expiration and expiration respectively;

FIG. 31 is a cross sectional view of a continuous venting embodiment ofthe assembly of FIG. 27;

FIG. 32 is an illustration of the internal structure of an exampleconduit suitable for implementation with a flexible divider assembly ofFIG. 27;

FIG. 33 is an illustration of a cross-sectional view of the internalstructure of an example conduit having a channel bend and extendedflexible divider;

FIG. 34 is a cross-sectional illustration of the internal structure of aconduit in and expiratory position having a flexible divider withopposed surface areas of different size;

FIG. 35 illustrates the structure of the conduit example of FIG. 34 inan inspiratory position;

FIG. 36 is an illustration of a divider having a surface with acontoured structure;

FIG. 37 is an illustration of a divider, with a normal bend;

FIG. 38 is an illustration of a channel divider linked to a vent coverin an expiratory position;

FIG. 39 is an illustration of the example divider of FIG. 38 in aninspiratory position;

FIG. 40 is a cross sectional illustration of a conduit with a duckbillversion of a divider of the present technology in an expiratoryposition;

FIG. 41 is a cross sectional illustration of the conduit of FIG. 40 inan expiratory position;

FIG. 42 is a cross sectional illustration of a divider with a ventingchamber with the divider in an expiratory position;

FIG. 43 shows the divider of FIG. 42 in an inspiratory position;

FIGS. 44 and 45 illustrate cross sectional views of an example couplerwith features similar to the conduit and flexible divider of FIG. 27;

FIG. 46 is a cross sectional illustration of a conduit similar to theconduit of FIG. 27 that includes a bypass channel;

FIG. 47 is a cross sectional illustration of a conduit similar to theconduit of FIG. 46 in series with a passive humidification material;

FIG. 48 is a cross sectional illustration of a conduit similar to theconduit of FIG. 46 in series with a further channel divider exchangersof the present technology;

FIGS. 49A, 49B and 49C are graphs that illustrate various flowcharacteristics of components of a common respiratory treatment systemrepresented by the circuit diagram of FIG. 49;

FIG. 50 is a graph illustrating venting with a traditional continuousventing orifice;

FIG. 51 is a pressure vs. flow graph illustrating example venting flowcharacteristics with an expiratory vent resistor such as the resistorsof FIGS. 15 through 19;

FIG. 52 is an example system configuration diagram showing a conduitwith a flexible channel divider coupled with a flow generator andpatient interface;

FIG. 53 is a graph illustrating venting with some implementations of thepresent technology;

FIG. 54 is a graph illustrating flow vs. time with respect to theconduit with a bypass channel such as the example of FIG. 46;

FIG. 55 is a signal graph illustrating patient flow estimation in asystem employing a conduit with a bypass channel such as the example ofFIG. 46;

FIG. 56 is a signal graph with flow and pressure data illustrating useof a traditional continuous-type vented mask;

FIGS. 57 and 58 are signal graphs with flow and pressure dataillustrating use of a flexible channel divider such as the divider ofthe conduit of the example of FIG. 26; and

FIG. 59 is a signal graph with patient interface humidity andtemperature data illustrating a comparison of a flexible channel dividersuch as the divider of the conduit of the example of FIG. 26 with atraditional continuous-type vented mask having no such divider.

DETAILED DESCRIPTION

As illustrated in FIG. 1, some embodiments of the present technology mayimplement an exchanger, such as in a conduit for air or breathable gasthat is directed to a respiratory system of a patient. The exchangerapparatus 100 may be coupled to or integrated with a patient interface108, such as a respiratory nasal mask, nose and mouth mask, full facemask, endotracheal tube, cannula, nasal prongs, nasal pillows, etc. Theexchanger 106 may be a component of a conduit assembly such as conduit101. The conduit may be coupled with an output of a flow generator, suchas a respiratory treatment apparatus, as discussed in other embodimentsherein so that the conduit may direct a respiratory treatment to thepatient. However, the conduit may more simply lead to atmosphere suchthat the conduit may more simply be used to condition ambient air for auser. In this regard, the exchanger may be implemented to condition theinspiratory flow with the expiratory flow or vice versa and mayoptionally do so without powered heating coils. Typically, the exchanger106 will separate, or form a portion of a barrier that divides orseparates, an inspiratory channel 102 and an expiratory flow channel 104of the conduit 101. In this regard, these channels can provide aunidirectional flow characteristic such that each channel may beimplemented to generally only conduct breathable gas in one direction.In this regard, in the case of the inspiratory channel 102, aninspiratory flow IF will be directed toward a patient interface end suchthat the inspiratory flow may be inspired by a user of the patientinterface 108. Similarly, in the case of the expiratory channel 104, anexpiratory flow EF will be directed away from the patient interface endsuch that the expiratory flow will have been expired by a user of thepatient interface 108.

In some embodiments, the unidirectional flow of the channels may bemaintained by optional valves. For example, at least one one-way valvemay control the flow through the channels. As illustrated in theembodiment of FIG. 1, an inspiratory one-way valve 110-I permits airflow in the direction (shown as IF) from atmosphere to enter theinspiratory channel 102 but would impede or prevent a reverse of suchair flow in the inspiratory channel. Thus, the inspiratory valve 110-Iwould be open during patient inspiration and closed during patientexpiration. Similarly, an expiratory one-way valve 110-E permits airflow in the direction (shown as EF) to atmosphere (away from patientinterface 108) so as to exit the expiratory channel 104 but would impedeor prevent a reverse of the illustrated flow through the expiratorychannel. Thus, the expiratory valve 110-E would be open during patientexpiration and closed during patient inspiration.

As a result of the configuration of the channels and the exchanger 106,the exchanger will be exposed to inspiratory flow and expiratory flowbut on opposing sides of the exchanger. In this sense, it will generallyhave an inspiratory side IS that is not generally exposed to expired airbut only fresh inspired air or gas and an expiratory side ES that is notgenerally exposed to fresh air before inspiration but only expired air.Thus, the exchanger may conduct or transfer a component of either theexpiratory gas or inspiratory gas to the other in association with thesesides. For example, the exchanger may be configured to conduct heat toserve as a heat exchanger. In such a case, warm expired air of theexpiratory channel 104 that may be warmed by the patient may contact theexchanger on an expiratory side ES. Thus, the expiratory air may warmthe exchanger 106. The exchanger, which may be formed or extruded of atemperature conductive material such as silver, copper, gold, aluminiumor a dust or composite of any of those materials etc., may conduct thatheat energy to the inspiratory side IS. The inspiratory flow IF of theinspiratory channel 102 may then contact the inspiratory side IS andabsorb the warmth that may be conducted, convected or radiated by theexchanger 106 if the inspiratory flow is cooler than the exchanger. Inthe case of a warm environment, the temperature of the exchanger mayeven potentially cool an inspiratory flow that is warmer than theexpiratory flow.

Thus, the patient's own respiration may be applied to condition thetemperature (e.g., heat or cool) of the inspired air through theexchanger. Moreover, since the inspiratory channel and expiratorychannels are divided by the exchanger, the exchange of temperature maytake place in a manner that minimizes potential for rebreathing ofexpired carbon dioxide. In this regard, the distinct inspiratory andexpiratory channels may permit the exchange without substantiallyincreasing dead space. Dead space may be considered the gas/space in theconducting areas of a respiratory system. In devices, such as theconduits of a respiratory treatment apparatus, it may refer to the samevolume/space through which a patient is breathing. In a single pathwaydevice where both inspiratory and expiratory gas flows to/from thepatient, the patient may re-breathe some of the air previously breathedout. Having a dual/separate inspiration and expiration pathways, thepatient is substantially consistently breathing in ‘fresh’ air from theinspiration pathway while breathing out to the distinct expirationpathway.

The exchanger, serving as a heat exchanger, may also reduce the outputrequirements or need for some heating components that are typicallyemployed to warm fresh inspired air. For example, the use of theexchanger may reduce the size needed for heating coils or the energyused by such heating coils to heat inspired air to a comfortabletemperature.

Similarly, in some embodiments, the exchanger may be implemented totransfer a moisture component of either the expiratory gas orinspiratory gas to the other. For example, expiratory flow EF maytypically include a degree of moisture that may be greater thanatmospheric air. The moisture of the expiratory flow may be absorbed bya material of the exchanger, such as a hydrophilic material, a capillarymaterial, a cellulose membrane, or a hydrogel, a polysulfone ether, abio-compatible polymer, etc. The moisture may condense on a surface of amaterial of the exchanger on the expiratory side ES of the exchanger106. The moisture may then transfer through the exchanger 106 to theinspiratory side IS. Inspiratory flow IF across the surface of theinspiratory side IS of the exchanger may then permit the moisture toevaporate into the inspiratory flow IF of the inspiratory channel. Insome embodiments the exchanger may be formed by a hydrophilic materialor coating on one side and a hydrophobic material or coating on theother such as to promote the absorption of liquid in one channel and theevaporation of liquid in the other. For example, the inspiratory channelside of the exchanger may have a hydrophobic material or coating and theexpiratory channel side of the exchanger may have a hydrophilic materialor coating. In the case of a warm environment, the humidity exchangermay even potentially cool an inspiratory flow that is warmer than theexpiratory flow. In the case that liquid is transferred from one flowchannel to another flow channel such as in the case where moisture iscondensed in the expiratory flow channel and transferred to theinspiratory flow channel in liquid form, the exchanger may takeadvantage of evaporative cooling as the liquid is vaporised by the flowin either channel, for example in the inspiratory channel, to cool theinspiratory gas.

Thus, the exchanger, serving as a humidity exchanger, may be implementedto condition the humidity of the inspiratory flow from the humidity ofthe expiratory flow. Moreover, since, the inspiratory channel andexpiratory channels are divided by the exchanger, the exchange ofhumidity may take place in a manner that minimizes potential forrebreathing of, expired carbon dioxide or without substantiallyincreasing dead space as previously mentioned. The exchanger, serving asa moisture exchanger, may also reduce the output requirements or needfor some humidification components that are typically employed tohumidify inspired air. For example, the use of the exchanger may reducethe quantity of reservoir water needed for a humidifier. Similarly, itmay also reduce the energy used by heating coils that heat water tohumidify inspired air.

In some embodiments, one or more materials of the exchanger may betreated or chosen for particular performance characteristics. Forexample, as previously mentioned, the exchanger may include coatings ofhydrophobic and/or hydrophilic materials. In some embodiments, amaterial of the exchanger may be coated to reduce carbon dioxidetransfer or diffusion through the material. For example, ananti-carbonation coating may be applied to an exchanger material such asa cellulose membrane or a poly sulfone ether material. Such a barriercoating may still permit a transfer of water while impeding a transferof carbon dioxide.

In some embodiments, the efficiency of the exchanger may be controlled,e.g., manually or automatically, to satisfy a patient's preferences. Forexample, in some embodiments the exchanger may be adjustable to permitgreater and lesser surface area of the exchanger to be contacted byinspiratory and/or expiratory flow. In such as case, greater surfacearea may permit more humidity or temperature transfer and less surfacearea may permit less humidity or temperature transfer. For example, inembodiments utilizing fins as discussed herein, an adjustment mechanism,such as a rotary control, slider, motor or solenoid, may withdraw orextend less or more of the area of fins into the channels of theconduit. Similarly, an adjustable cover(s) may extend or retract todifferent degrees to provide a movable barrier or insulator on one ormore portions of the exchanger to change the contact area of theexchanger that can contact the flow in one or more channels of theconduit to impede the exchanger's efficiency to varying degrees. In somecases, automated control of the adjustment mechanism may involveevaluation, such as by a processor-based controller, of signals from oneor more sensors, such as a humidity and/or temperature sensor that maybe located proximate to either channel of the conduit, in the setting ofthe portion or size of the area of the exchanger that can participate inthe exchange transfer. The controller or processor, which may also be acontroller of a flow generator, may be configured and adapted toimplement the control methodologies. Thus, the controller may includeintegrated chips, a memory and/or processor control instructions or datain an information storage medium. For example, programmed instructionsencompassing the control methodology may be coded on integrated chips inthe circuits or memory of the device or such instructions may be loadedas software or firmware using an appropriate medium containing theinstructions or data.

As previously mentioned, some embodiments of the exchanger apparatus100, whether implemented for temperature or humidity exchange or both,may be configured for different respiratory purposes. For example, asillustrated in FIG. 2, the inspiratory channel 102 may include asupplemental gas source input port 212. In such an embodiment, the inputport 212 may include a coupler for coupling with a supply tube of asupplemental gas source, such as an oxygen source. In such anembodiment, the expiratory flow EF may then serve to condition theinspiratory flow IF that includes the supplemental gas flow SGF and airthrough the implementation of the exchanger 106.

The embodiments of FIGS. 3, 4 and 5 illustrate various implementationsof the exchanger apparatus 100 and may include a respiratory treatmentapparatus that includes a flow generator 314. As illustrated in theversion of FIG. 3, a supply conduit 316 from an output of the flowgenerator (e.g., a blower output) may be coupled with a pressurizedchamber 320 having a vent 318 for expiration. The supply conduit maydeliver a flow of breathable gas, e.g., air, at a pressure aboveatmospheric pressure that is generated by the flow generator to thepressurized chamber 320. The vent 318 may serve as a washout vent orflow limiter. The pressurized flow from the flow generator may passthrough the inspiratory channel 102 but not the expiratory channel 104when the patient's inspiration opens the inspiratory valve 110-I.Patient expires through the expiratory channel 104 when the patient'sexpiration increases the pressure in the expiratory channel above thepressure of the chamber 320. The expired flow then proceeds through thechamber to exit the vent 318 to atmosphere. Thus, in this embodimentboth air to be inspired and expiratory air traverse through chamber 320.

The embodiment of FIG. 4 is similar to that of FIG. 3. However, in thisversion, the chamber 322 does not directly couple with the supplyconduit 316. The supply conduit 316 is coupled to an input of theinspiratory channel 102. The vent 318, via chamber 322, is coupled tothe expiratory channel. Accordingly, in this embodiment, expired airfrom the expiratory channel is not introduced to any conduit thatsupplies breathable gas to the inspiratory channel 102.

The embodiment of FIG. 5 is similar to the embodiment of FIG. 4 and maybe implemented without a flow generator as shown. However, in theillustrated embodiment, one or more of a Starling resistor 420, avariable or adjustable vent 422 or any of the flow resistors describedin more detail herein, may replace the one-way valves. For example, asshown, a Starling resistor 420 may be implemented in a flexible portionof the supply conduit 316 to regulate flow into the inspiratory channel.Similarly, an adjustable vent 422 implemented with a Starling resistor420 may serve in lieu of the expiratory valve 110-E. Any known variableor adjustable vent may be implemented. For example, any of the ventassemblies described in U.S. Provisional Patent Application No.61/534,044, filed on Sep. 13, 2011, the entire disclosure of which isincorporated herein by reference, may serve as the adjustable vent 422.By operation of the resistor(s) and/or controlling an adjustable vent,flow through the channels may be regulated to direct the inspiratoryflow through the inspiratory channel 102 and the expiratory flow throughthe expiratory channel 104. For example, pressure swings in the mask maybe detected to set the adjustable vent for greater flow duringexpiration to permit expired air to flow through the expiratory channelto the adjustable vent during expiration. Based on the pressure swings,the adjustable vent may then be set for less or no flow duringinspiration so as to permit inspiration flow from a flow generatorthrough the inspiratory channel to the patient for inspiration.

Operation of the Starling resistor 420 may be considered in conjunctionwith the illustrations of FIGS. 5A and 5B. In this embodiment, theStarling resistor in a conduit 416 employs a chamber link conduit 420C.The chamber link conduit 420C provides a pneumatic link to an innerflexible chamber IFC formed by the flexible membrane 420M within theconduit 416. As illustrated in FIG. 5A, when a lower pressure LPcondition in the conduit exists proximate to the link opening end420C-LO of the link conduit 420C with the higher pressure HP conditionin the conduit on the opposing side of the flexible chamber IFC, theflexible chamber will contract to permit flow through the channel of theconduit. As illustrated in FIG. 5B, when a higher pressure HP conditionin the conduit exists proximate to the link opening end 420C-LO of thelink conduit 420C with the lower pressure LP condition in the conduit onthe opposing side of the flexible chamber IFC, the flexible chamber willexpand to resist or impede flow through the channel of the conduit.Accordingly, depending on the location of the link opening end 420C-LOof the link conduit 420C, the conduit with the Starling resistor may beselectively implemented to limit flow to either inspiratory flow orexpiratory flow as previously described. Alternatively, the membranechamber may be selectively activated by a pneumatic link to an output ofa flow generator rather than using the link conduit 420C as illustratedin FIG. 5.

FIG. 6 illustrates a further example exchanger embodiment for bothhumidification (labelled as “M” in FIG. 6) and temperature (labelled as“H” in FIG. 6) exchange. In this embodiment, the exchanger includes aheat exchange portion having sets of fins that may be configured fortemperature exchange. The fins may extend into the inspiratory channel102 and/or expiratory channel 104 to increase the surface area by whichthe conduit flow contacts the exchanger. In this example, one or moreinspiratory fins 660-I extend within the inspiratory channel and one ormore expiratory fins 660-E extend within the expiratory channel 660-E.Flow passing on either side of each fin creates additional flow pathswithin each channel such that flow may then contact two sides of one ormore of the fins permitting a greater transfer of heat energy. By usingnarrow width fins that have their lengths (“L”) positionedsubstantially, parallel to the flow of the channel, the flow through thechannel may pass more easily along the fins to increase the surfacecontact area while not introducing a significant resistance to flowthrough the fin portion of the channel. A further example of such anexchanger is illustrated in FIG. 8.

While the fins may be located substantially directly across the channelbarrier 661 between the inspiratory and expiratory channels, in thisembodiment, the fins may include a transverse portion 662 that connectsthe inspiratory fins with the expiratory fins. As illustrated in theembodiment of the FIG. 6, the transverse portion may extend along thechannel barrier and may form a portion of it, and it may be generallyparallel to the flow of each channel. The transverse portion can permitthe expiratory fins to be located more proximate to a patient interface108 end of the expiratory channel and the inspiratory fins to be locatedless proximate to the patient interface 108 end of the inspiratorychannel. Typically, the transverse portion will be formed of the same orsimilar heat conducting materials as the fins to permit the transfer ofheat energy between the sets of expiratory and inspiratory fins.

Optionally, the exchanger 106 also includes a humidity exchange portion664. For example, the humidity exchange portion may be located withinone or more apertures of the exchange portion. As previously described,the humidity exchange portion in some embodiments may include acapillary section configured with fine bores to permit a capillarytransfer of liquid from the expiratory channel to the inspiratorychannel through or between the transverse portion. An example of acapillary section 776 for a humidity exchange portion is alsoillustrated in FIGS. 7, 8 and 9. Optionally, the humidity exchangeportion may alternatively, or also, be located between the expiratoryfins and/or the inspiratory fins. In the exchanger version of FIG. 8,the capillary section 776 includes fine bores that extend through toapertures between the fins 660-I, 660-E as well as on the transverseportion 662.

In the exchanger of FIG. 9, the capillary section 776 may be limited tothe transverse portion. As an alternative to fins, the exchanger mayinclude temperature conducting blocks 960-I, 960-E. Each block mayinclude a plurality of flow passages that may be substantially parallelto each other. The flow passages may be formed by holes through eachblock. In such a case, the holes of the block will be larger than theapertures of the capillary section so as not to substantially impedeflow through the block. Thus, an inspiratory block 960-I may permit theinspiratory flow to traverse through its inspiratory block passages992-I for a temperature exchange with inspiratory flow. Similarly, anexpiratory block 960-E may permit the expiratory flow to traversethrough its expiratory block passages 992-E for a temperature exchangewith expiratory flow. The additional passages through the holes in eachblock of the channel can permit an increase in surface contact area withthe heat conducting material of the block and thereby a more efficienttransfer of heat energy. Although holes are shown through the blocks,the structure of the block may be replaced by a matrix or mesh channelhaving multiple pathways through a portion of the exchanger to otherwiseincrease the contact area of the exchanger. Moreover, although theblocks are illustrated as rectangular in FIG. 9, the blocks may beshaped to conform to the shape of any conduit with which the exchangeris implemented.

To this end, some exchanger embodiments of the present technology may beimplemented in conduits having a generally tubular form such as a tube.However, other conduit configurations may also be implemented. Forexample, the channels and exchanger may be implemented as an integratedconduit of a patient interface. In FIGS. 10A, 10B, 11, 12, 12A and 13some example tubular exchanger conduits are illustrated. FIGS. 10A and10B show cross-sectional views of an example of a pleated exchanger106P. The exchanger 106 of this embodiment is implemented with aplurality of folds 1070 each with a crease 1072 that runs generallyalong or parallel to the flow through the channels of the conduit orparallel to the length of the conduit. As illustrated in the figures, insome embodiments, the exchanger may be inserted into a top conduitportion 101-T and a bottom conduit portion 101-B. When assembled, asillustrated in FIG. 10B, the top conduit portion and exchanger may forma first channel for conduit flow, such as the inspiratory channel 102.Similarly, the bottom conduit portion and the exchanger may form asecond distinct channel for conduit flow, such as the expiratory channel104. In this way, the folds of the exchanger 106 can provide a greatercontact surface area for the exchanger along the channels.

In the cross-sectional view of the embodiment of FIG. 11, the exchanger106 is formed as a conduit with the exchanger material serving as thesurface structure of the conduit. Thus, the exchanger may be formed witha tubular shape such as a tube. The tubular exchanger 106 may bepositioned within a larger conduit. In such an embodiment, the flow ofouter channel may substantially flow along the circumferential peripheryof the exchanger to increase surface area contact. For example, theinner surface of the outer conduit 101 and the outer surface of theexchanger 106 may form the inspiratory channel 102. In such a case, theinner surface of the exchanger would then form the barrier of theexpiratory channel 104. This is the example illustrated in FIG. 11.However, in some embodiments, the inner surface of the outer conduit 101and the outer surface of the exchanger 106 may form the expiratorychannel 104. In such a case, the inner surface of the exchanger wouldthen form the barrier of the inspiratory channel 102. In suchembodiments, the exchanger may also be implemented with folds and/orwith fins. For example, as illustrated in the cross sectional view ofthe exchanger conduit of FIG. 12, a plurality of heat conducting finsmay extend across the channels to form inspiratory fins 660-I andexpiratory fins 660-E. By way of further example, as illustrated in thecross sectional view of the exchanger conduit of FIG. 12A, a pluralityof folds of the exchanger provide a circumferential periphery of aninner channel that may be the inspiratory channel 102, as well as aninner boundary for an outer channel that may be the expiratory channel104.

In some embodiments, the inspiratory channel and/or expiratory channelmay be implemented in a less linear fashion from the linear versionshown in FIG. 8. For example, the channels and the exchanger may beimplemented with a spiral or helical configuration to increase surfacecontact area. In some such embodiments, an inner channel, such as aninspiratory channel formed by the exchanger, may spiral centrallythrough a more linear outer expiratory channel of a conduit. In afurther example illustrated in FIG. 13, the channels may both spiraltogether in a helical configuration. For example, an exchanger 106 thatforms a divider barrier that splits the conduit along its length, may betwisted along the conduit length to form a spiral barrier such thatinspiratory channel 102 and expiratory channel 104 both spiral onopposing sides of the conduit along the conduit length. Such a spiralformation may yield an increase in exchanger surface contact area andmay promote contact with the exchanger by creating flow turbulence alongthe exchanger.

In some embodiments, the expiratory and inspiratory fins of theexchanger may serve as channel dividers such as in the exampleembodiment of FIG. 14. In this embodiment, the channels may beinterleaved by fins that extend substantially across the cross sectionof the conduit. In this version, each fin divides an inspiratory channel102 and an expiratory channel 104 such that the inspiratory channel andexpiratory channel are on opposing surface faces of each fin.Optionally, grooves 1447 that extend along length of the conduit mayprovide an escape vent to atmosphere for expiratory flow from theexpiratory channels. Thus, each groove 1447 may be a cut through theconduit 101 to an expiratory channel 104. The expiratory channels 104may be closed at a closed end 1449.

In some embodiments, it may be useful to supply moisture to an exchangerbefore or during use. For example, a fine bore liquid supply tube mayextend from a reservoir, such as a bag, bottle or a container of arespiratory treatment apparatus. The tube may be configured with one endat or in a material of the exchanger to drip a liquid (e.g., water) onthe exchanger. The small tube may operate by the Venturi effect to addwater from the reservoir into the inspiratory flow path or theinspiratory side of the exchanger to humidify the inspiratory flow. Forexample, as water evaporates from the inspiratory side of the exchangeras a result of the inspiratory flow, more water from the liquid supplytube may then drip into the exchanger.

In some cases, the exchanger may include or be near a heating element,such as for warming inspired air. For example, a thermoelectric devicesuch as a Peltier device may be included in a channel of the conduit ofthe exchanger. The thermoelectric device may be powered by an internalor external battery or other power source, such as the external powersource of a flow generator.

Expiratory Venting

In the case of implementing distinct inspiratory and expiratory channelswith a patient interface that may provide a pressure treatment, such asfor providing a pressure above atmospheric pressure during expiration tostent a patient airway, it may be useful to include a device to regulatepressure within the expiratory channel particularly if the inspiratorychannel to a flow generator will be closed during patient inspiration.For example, the channel may be implemented with an expiratory flowresistance component to provide a level of resistance that raises ormaintains some pressure above atmospheric pressure in the expiratorychannel, and as well as the patient interface, during expiration. Such aresistance/impedance component may be designed by varying constructionsof the length/shape of the pathways and the size/width of the pathways.Examples may be considered in reference to the expiratory flow resistorsillustrated in FIGS. 15 to 25, which might or might not be implementedwith any of the expiratory channels or vents described herein, and mightor might not be implemented with any of the exchangers described herein.This style of venting, such as the venting described in reference to thecomponents of FIGS. 15-18, may be particularly suited to a gas deliverysystem with a constant blower rotational speed, or a high impedancecircuit, for example, a long and narrow tube to allow for less therapypressure fluctuation.

In the embodiment of FIGS. 15 and 16, a rigid vent cover 1580 may bemovable on a pivot 1581. A biasing member, such as a spring 1582, may becoupled to the rigid vent cover 1580. The biasing member provides a biasto the rigid vent cover 1580 such that it may be preloaded with aresistance when closed as shown in FIG. 15. The bias may provide adesired load or pressure threshold that will permit a desired level ofpressure to build or be maintained in the expiratory channel 104 duringpatient expiration before the rigid vent cover will yield to a patientgenerated increase in expiratory pressure. Similarly, the size of theopening permitted by the biased vent cover may be regulated by thebiasing member to maintain a level of pressure within the expiratorychannel 104 during at least a portion of patient expiration even asexpired flow exits the expiratory channel 104 through the vent 318 whenopen as illustrated in FIG. 16.

The expiratory flow resistor embodiment of FIGS. 17 and 18 operates in asimilar manner to that of the embodiment of FIGS. 15 and 16. In thisembodiment, a flexible flap may serve as the vent cover and might notutilize a pivot. For example, a flap holder 1584, such as an abutment ofthe conduit wall, can ply the flap member against the vent to bias theflexible flap 1585 with a tension into its closed position asillustrated in FIG. 17. The bias must be overcome by expiratory pressurein the expiratory channel 104 for the expired air to escape from thevent 318.

In other words, in these embodiments, the bias of the cover or flexibleflap of the vent may be chosen so that the cover or flap will start toopen when the pressure differential times the area of the flap or coveris greater than the compression force in the spring, (or the deflectiontimes the spring constant of the flap). Thus, in typical embodiments,this means that below this prescribed pressure differential, which mayserve to provide a stenting pressure during expiration, the vent will beclosed. Consequently, it will also be closed during inhalation.

In some cases, the bias may be chosen to yield venting with the pressure(P) and flow (Q) characteristics as illustrated in FIG. 51. For example,

If pressure is less than ‘x’; P=K1*Q²+K2*Q

If pressure is greater than ‘x’; P=m*Q+b;

Where P is pressure, Q is flow, and ‘b’ may be equal to a nominaltherapy pressure, and may be tuned by the amount of pretension.

It may be desirable to have ‘m’ as small as possible, for example bymaking the orifice large and coefficient of stiffness small.

The expiratory flow resistor of the embodiment of FIGS. 19 and 20 maypermit another similar expiratory pressure stenting. This embodiment maypermit pressure to be maintained in the expiratory channel 104 throughpressure manipulation of a membrane that may be configured as a membraneballoon 1990. Operation of a flow generator may pressurize the membraneballoon 1990 through a membrane pressurization chamber 1991 or conduit.The chamber 1991 may be coupled with the supply conduit 316 to the flowgenerator 314 of respiratory treatment apparatus. Pressurization of themembrane balloon 1990 permits the membrane to expand to cover or contactone or more vent apertures of the vent 318 during inspiration asillustrated in FIG. 19. During this inspiratory phase, the inspiratoryone-way valve 110-I will be open and flow moves through the inspiratorychannel 102 which may optionally include exchanger 106. However, whenthe patient expires into the patient interface 108, the inspiratory oneway valve 110-I will close as illustrated in FIG. 20. When the pressureof the expiratory chamber 104 exceeds the pressure in the chamber 1991,the membrane balloon 1990 will deform away from the apertures so as toopen the apertures of the vent 318. Since the chamber 1991 ispressurized by the flow generator 314, control of the flow generator, inconjunction with the characteristics of the membrane balloon 1990 andchamber 1991, can permit the setting of an expiratory stenting pressureeven though the flow generator does not supply pressure directly to thepatient's airways during expiration.

FIGS. 21 and 22 illustrate another membrane structure that may serve asan expiratory resistor similar to the embodiment in FIGS. 17 and 18. Theflexible flap 2185 may serve as a barrier between atmospheric air andair in the airpath of the conduit 101 via an aperture of the conduitthat allows coupling of therapy pressure and atmospheric pressure. Therigid flap holder 2184 in this embodiment may include one or moretensioning bars 2184P and a holder ridge 2184R that may be integratedwith a wall of the conduit 101 to bias the flexible flap. The flexibleflap 2185, which may be a resilient membrane under a preloaded tensiondue to the configuration of the tensioning structures, may flexdepending on the pressure within the expiratory channel 104. In thisembodiment, the membrane is inserted between the bars. Opposing ends ofthe membrane may contact an external side of the conduit and an internalside of the conduit. When the flap opens so as to separate from itscontact with a rigid wall of the conduit 101 at a high pressure vent endHPVE or a low pressure vent end LPVE, the opening may serve as a vent318. As explained in more detail herein, the HPVE end permits an airexhaust for a high pressure condition and the LPVE end permits an airintake for a low pressure condition. As shown in FIG. 22, someembodiments of the expiratory resistor conduit may be configured as anelbow, such as an elbow for a patient interface device or an elbow forbetween an air delivery conduit and a flow generator. However, it mayalso be implemented in other conduits such as the exchanger conduitsdiscussed throughout this specification.

Such a flow resistor may also serve a purpose of reducing pressureswings in the patient interface (e.g., mask) when used with a pressuretreatment device (e.g., CPAP therapy generator). The flexible membraneflap impedes the coupling of the system air path to atmosphere. Theimpedance changes according to the deflection of the flexible membrane.The deflection of the flexible membrane flap is a function of thepressure differential between the therapy pressure side of the membrane(e.g., in the expiratory channel 104) and the atmospheric side of themembrane. The preloaded tensioning of the flexible membrane flapprevents deflection from the wall of the conduit until the therapypressure in the conduit rises to overcome the preload so as to open atthe high pressure vent end HPVE. In such a case, the membrane at thehigh pressure vent end HPVE would flex outwardly from the conduit andpermit an air exhaust from the conduit. The preloaded tension of theflexible membrane flap may also prevent deflection from the wall (e.g.,at holder ridge 2184R) of the conduit until the pressure in the conduitdrops enough to overcome the preload so as to open at the low pressurevent end LPVE. In this case, the membrane flap at the low pressure ventend LPVE would extend inwardly into a chamber of the conduit to open thevent 318 and permit air intake into the conduit. These operations canenable ‘standard’ venting up to a set pressure beyond which the ventopens to allow increased flow to atmosphere in such a way that thetherapy pressure remains constant within the conduit for respiratorystenting. The operations can also allow the vent to prevent therapypressure from becoming negative.

There may be several benefits from such a venting component. It mayreduce pressure swings that may be associated with the use of narrowtubes. It may enable the use of narrower tubes. It may reduceinefficient venting (particularly during inhalation). It may reducetotal airflow and/or flow generator power when compared to vents thatremain constantly open. It may similarly reduce flow through ahumidifier so as to thereby increase humidification time limits that areassociated with fixed water reservoir size. It may also serve to protectagainst over pressure and/or asphyxia because it can serve as ananti-asphyxia device. These types of vent may be more suitable tocontinuous positive airway pressure than bi-level therapy as theoperating pressure may be determined by the amount of pretension.

The expiratory resistor embodiment of FIGS. 23 and 24, which is similarto the embodiment of FIGS. 19 and 20, may readily permit expiratorystenting pressure to be maintained in an expiratory channel despite anabsence of flow against the patient's airways from the flow generator314 during expiration. A membrane 2390 flexible cover, which may beresilient flexible material, may be positioned over apertures of a vent318. The cover membrane may serve as a part of separator for aninspiratory channel 102 and an expiratory channel 104. As illustrated inFIG. 23, during inspiration, the membrane 2390 is maintained in a coverposition against the apertures of the vent 318 due to the pressure ofthe inspiratory channel and/or due to the shape memory of a resilientmaterial of the membrane. Inspiratory flow. IF, which may be generatedby a flow generator 314, may proceed through inspiratory channel 102 andthe inspiratory one-way valve 110-I to a patient interface 108 duringinspiration. Closure of the inspiratory valve 110-I during expiration,as shown in FIG. 24, permits pressure to build at an expiratory channel104 side of the membrane. When the pressure from expiration in theexpiratory channel 104 side of the membrane overcomes the treatmentpressure generated by a flow generator at the inspiratory channel sideof the membrane, the flexible membrane 2390 will deflect or expand topermit expiratory flow EF out through the vent 318. Optionally, portionsof the flexible membrane may include a material of an exchanger (notshown).

The embodiment of FIGS. 25A and 25B is similar to that of FIGS. 23 and24. However, in the embodiment of FIGS. 25A and 25B, the flexiblemembrane 2590 includes an expiratory flow stopper 2592. The stopper 2592may include one or more plugs 2594 that may be configured for closingvent apertures 2596 of vent 318. For example, plugs may be configuredfor selectable insertion within the vent apertures 2596. Optionally,such plugs may be tapered. As illustrated in FIG. 25A, the resiliency ofthe flexible membrane and/or the pressure from a flow generator at aninspiratory channel 102 side of the membrane or stopper may maintain theflow stopper 2592 in a closed or partially closed position duringinspiration. During patient expiration, as illustrated in FIG. 25B, anincrease in pressure in the expiratory channel 104 side of the membrane2590 will shift or flex the membrane and the flow stopper when theincrease in pressure overcomes the pressure (e.g., flow generatedtreatment pressure) at the inspiratory channel 102 side of the membrane2590. This shift of the membrane and stopper will withdraw the plugs2594 from within the vent apertures 2596 to permit venting of expiratoryair. Since the expired flow must overcome any membrane resiliency and/orthe treatment pressure at the inspiratory channel 102 side of themembrane, a stenting pressure may be maintained in the expiratorychannel 104 as well as in the patient interface and patient respiratorysystem.

ADDITIONAL EXAMPLE EMBODIMENTS

Further example embodiments for conduits of the present technology thatcan be implemented with an exchanger are illustrated in thecross-sectional views of FIGS. 26, 27, 28, 29, 30, 31, 32 and 33. Inthese examples, a flexible channel divider 2607, such as a membrane, mayserve to regulate inspiratory flow in the conduit 2609 to dynamicallycreate the inspiratory and expiratory flow channels and may providedynamic expiratory venting. In some cases, the conduit 2609 may becoupled proximate to a patient interface (e.g., mask 108) at theopposite end of a supply conduit 316 from a flow generator 314 asillustrated in FIG. 52. Implementation of such a divider may permit areduction of total flow through a mask, such as when compared to apatient interface using a continuous vent, and may thereby increaseefficiency of humidifiers, oxygen sources and flow generators. The forcerequired to breath against the divider may also permit an elevatedexpiratory stenting pressure that may be adjusted by choosing a suitablevent size and divider flexibility. This can also reduce the work of aflow generator during expiration. Similarly, the divider may reducepressure swings in the conduit leading to a patient mask such that itmay reduce the burden on a flow generator to compensate for the pressureswings. Optionally, the flexible divider may also be implemented withcomponents or materials previously discussed such that the moveabledivider may also serve as an exchanger. Generally, the mechanicalproperties of the flexible divider can be tuned by varying thickness orother dimensions and its material properties, such by changing itsstiffness, density and damping characteristics.

For example, as illustrated in FIG. 26, the channel divider 2607 may beimplemented within a conduit 2609. Such a flexible divider may have afixed end FE and a deformable portion DP. The fixed end may be coupledwith the conduit wall 2609W. The divider 2607 is also substantiallyproximate to a venting portion 2611, which may be formed by a pluralityof apertures for expiratory venting, so as to permit the divider toserve as a cover of the venting portion. The pneumatic impedance of theventing apertures may be controlled in the design by their geometry,such as their length and cross-sectional area, as such the impedance ofthe apertures may provide additional pressure to the divider duringexpiration. This can assist with the activation of the divider at thebeginning of expiration and prevent the divider from blocking theapertures during periods of small expiratory flow, such as the end ofexpiration.

Optionally, the conduit may include a conduit bend 2609B such that thewall of the conduit and the channel of the conduit deviate from astraight direction. In such an embodiment, the divider may extend alongthe wall from one portion of the conduit with a first channel CA thathas a first angle into the bend portion of the conduit that has a secondchannel CB at a second angle. The extension of the divider across thebend from the first channel to the second channel creates a lip end LEon the flexible portion DP of the divider where the divider deviatesfrom the conduit wall. As described in more detail herein with referenceto FIGS. 28, 29 and 30 concerning the operation of the assembly, the lipend LE may assist in the dynamic activation of the channel divider.Generally, the lip end LE of the divider is more proximate to thepatient or user end 2609UE of the conduit, such as where a mask may becoupled, and the fixed end FE of the divider is more proximate to theair or gas supply end 2609ASE of the conduit, such as where a flowgenerator output may be coupled.

With respect to the dynamic creation of the inspiratory and expiratorychannels, the divider may create an inspiratory channel between a firstside of the conduit and a first side of the divider and an expiratorychannel between the opposing side of the conduit and the opposing sideof the divider when the divider traverses between the opposing sides ofthe conduit during use. The divider may do so by traversing across theconduit from one side to the opposing side. Typically, such a transitionof the divider to the fully open expiratory position as shown in theexample of FIG. 30 from the fully open inspiratory position shown inFIG. 28 (and the opposite transition) is very quick. Generally, thedivider will be in these fully open positions during each respectivephase of respiration. This reduces the velocity and turbulence of theair flow and results in lower noise, which can be particularly importantfor use during sleep.

The flexible divider may be configured such that during inspiration theforces acting on the divider force it into a position that obstructs, orimpedes venting to atmosphere. The forces include the static and dynamiccomponents of pressure acting on the divider surfaces and the force dueto gravitational acceleration acting on the mass of the divider. Thedivider can be light to minimize the later forces and other dynamicacceleration effects. The flexible divider may also be configured suchthat during expiration the forces acting on it force it into a positionthat obstructs or impedes flow to the flow generator (preventing orreducing the possibility of rebreathing).

Since the divider may be flexible, the response of the divider may becontrolled by setting different pressures with the flow generator.Moreover, the level of flow may be controlled or dictated by the user.For example, if the patient is not breathing on the system, the flow bythe divider (e.g., from the flow generator) may be zero. The higher thepatient's expiration pressure, the more open the expiratory channelbecomes, which provides larger flow, less turbulence and less noise.Accordingly, the pressure may be controlled by the flow generator butthe patient may dictate the flow.

Generally, the position of the divider may be determined by theequilibrium of forces acting on it. One of the main contributors to thisequilibrium position is the therapy pressure times the surface area ofthe divider which is exposed to the therapy pressure. Another maincontributor to the equilibrium is the pressure coming from the flowgenerator times the surface area of the divider exposed to thatpressure. If we neglect all other forces, by Newtons Second Law, themass times the acceleration of the divider will equal the differencebetween the two main forces. As such, the divider will accelerate towardthe direction of the side of the lower pressure. As this happens, theexpiratory impedance will change and this will result in the therapypressure changing, such that a new equilibrium is reached. When theforces are equal the divider will be stationary. When the respiratoryflow changes the equilibrium position of the divider will change andalter the expiratory resistance to equalise pressures on each side ofthe divider.

By reducing or ceasing venting flow during inspiration, which thedivider is capable of achieving by intermittent closing of ventingapertures as discussed herein, the total flow through the supply conduitmay be reduced. Reducing vent flow during inspiration reduces the amountof flow that the flow generator needs to produce to maintain therapypressure. Eliminating vent flow can reduce the amount of flow the flowgenerator needs to produce by more than 50%. This means for a constantspeed flow generator, the pressure drop can be (significantly) less. Thepneumatic efficiency of the flow generator system will be increased.Moreover, a pressure controlled flow generator will need to compensateless for the supply conduit (e.g., tube) loss. Reducing flow generatorflow also makes the full system more energy efficient and quieter. Thismay also permit the conduit to be employed in systems that deliversupport using narrow, high impedance supply conduits.

Moreover, in the absence of inspiratory venting, the inspiratorypressure drop or the need to compensate for an inspiratory drop toimprove pressure swings may be reduced.

Reduced venting also may reduce the drying effect on the patient'sairways since flow is only provided when the patient breathes. It mayalso permit more natural breathing at higher pressures.

The action of the divider and reduced total flow may also have theeffect of increasing humidity in the patient interface. As illustratedin FIG. 59 showing humidity and temperature data, venting with thedivider over time may promote a higher degree of humidity when comparedto a traditional continuous vent type mask. On average, the dividercould provide a level of humidity approximately 10% higher than thehumidity provided using a standard continuous vented mask. As a result,it can also improve the effectiveness of any exchanger or HME materialsuch as if implemented in the configuration of FIG. 47. Generally, thenatural humidity in the system can be improved with the use of thedivider.

The reduction inflow and the resulting retention of moisture can meanlonger humidifier operation. This can reduce the need for refilling ahumidifier with water, or permit a smaller capacity humidifier designwhen the divider is implemented with an active humidifier. Similarly,oxygen delivery can be more efficient. Reduced flow generally results inless turbulent noise both at the vent, and in the flow generator system.Reduction in flow related pressure losses can mean lower motor speeds,and result in less machine noise and longer machine life. A moreefficient flow generator system can result in less power being requiredto operate the system. For a portable device, this could permit use ofsmaller battery or a battery with less capacity, or can permit longerbattery operation.

The reduced flows with the conduit can permit a more natural feelingtherapy. Continuous venting is often perceived by the patient in theform of noise and vibration. The continuous venting flow also has adrying effect on the airway, requiring use of a humidifier for some. Theflexible divider vent can permit users to experience a more naturalfeeling therapy even when the pressure is increased, since the userdetermines the amount of flow in the system. This can result in reduceddrying of the airways and reduce or remove the need for a humidifiersystem.

Accordingly, returning to FIG. 26, the venting portion 2611 may includea plurality of apertures. These apertures may be optionally boredthrough a wall of the conduit or be applied as a grate component to theconduit. The apertures may run perpendicular to the inner conduitsurface as illustrated in FIG. 26. However, in some embodiments that mayimprove flow through the venting portion, the apertures may be at anoblique angle relative to the surface of the conduit. For example, asillustrated in FIG. 27, the apertures may deviate from perpendicular soas to angle the channel of each aperture toward the lip end of thedivider. In some embodiments a diffuser may be applied over the ventingportion.

Example aperture angles may be considered with reference to imaginaryaxis lines AXA shown in FIGS. 26, 27 and 32. For example, as illustratedin FIG. 26, apertures of the venting portion 2611 may be formedgenerally perpendicular to the flow path or inner surface of the channelof the conduit 2609. In some cases, as illustrated in FIG. 27, thechannels of the inner surface of the apertures of the venting portion2611 may be formed at an obtuse angle with respect to the inner surfaceof the channel of the conduit and direction of expiratory patient flow.In such a case, the direction of expiratory airflow from the user end2609UE through the conduit will not deviate too substantially betweenthe direction of the channel of the conduit and the direction of thechannel of the aperture. In such a case, patient expiratory turbulencethrough the venting portion may be minimized. However, in some cases,expiratory patient airflow turbulence may be increased with theimplementation of apertures with channels that deviate at an acute anglefrom the inner surface or channel of the conduit with respect to thedirection of expiratory flow as illustrated in FIG. 32. The expiratoryairflow turbulence created with such acute angled apertures may help toaffect a more responsive action (e.g., quicker) by the divider toexpiratory flow at lower flows. As such, the divider may stay in an openposition with respect to the venting portion longer as the rate ofexpiratory flow recedes (e.g., at or nearer to the end of expiration) oropen faster with initial expiration. Thus, a smaller expiratory flowforce may continue to deflect the divider. In addition, the accelerationrequired to turn the flow direction to the new angle requires a reactionforce of the divider. This reaction force tends to open the path to theaperture, and thus reduces the impedance of the path, hence lowering thetherapy pressure, and allowing the divider to remain in the openposition longer. The amount of reaction force may be tuned by tuning theangle of deviation of the flow path. This may be understood bycalculating the reaction force according to the equationF=dm/dt(v ₂ −v ₁)Where F is the force vector (having magnitude and direction), dm/dt isthe mass flow rate of the gas, v₁ is the flow velocity vector (havingmagnitude and direction) of the fluid approaching the divider asillustrated in FIG. 46. And v₂ is the flow velocity vector (havingmagnitude and direction) of the fluid leaving the divider as illustratedin FIG. 46. It can be seen from the equation that as the angle betweenv₁ and v₂ increases the reaction force also increases. Therefore, insome embodiments it may be desirable to divert the expiratory gas by alarge angle (illustrated as angle AN1 in FIG. 46) in order to exert asuitable force on the divider.

Optionally, the conduit may also include a divider support 2615, such asone or more ridges, fins or ribs that may project or extend into thefirst channel, CA, along the conduit wall that is on a side opposite tothe side of the conduit where the membrane is fixed. The fins, ribs orridges may be generally parallel and extend longitudinally along theflow path of the conduit. Such a membrane support may help to preventthe membrane, from over flexing as discussed in more detail herein. Anexample of an internal structure of the conduit assembly includingseveral rib or fin-type membrane supports 2627 is illustrated in FIG.32. This embodiment also employs a divider shelf 2609S that may beformed along the conduit wall. The divider shelf provides a seat againstwhich a peripheral edge of the divider may seal during expiration asdiscussed herein in reference to FIG. 30.

The length of the divider 2607 from its fixed end FE to the lip end LEmay also be particularly chosen to prevent over flexing that in someinstances might cause jamming of the divider in the channel. Forexample, in a typical embodiment the length will be greater than thechannel or conduit width (shown as CW in FIG. 26) but may besubstantially longer. For example, the range of such a length may be onthe order of 1.25 to 8 times the channel or conduit width CW of theparticular channel across which the divider will flex. In some cases, itmay even be larger.

In some cases, the divider may be configured with a normal position suchthat it will, in the absence of flow or pressure forces associated withflow generator operation, resiliently remain slightly deviated away fromthe venting portion 2611 as shown in FIG. 26. This marginal deviationmay permit flow through the venting portion such that it may serve as ananti-asphyxia device. Thus, in the absence of any pressure generated bythe flow generator (e.g., a flow generator failure or turned off flowgenerator), the channel divider will return to this normal “deviated”position to permit a patient to breathe through the venting portion 2611and the flow generator during inspiration. Such a deviation may, forexample, be achieved by the resiliency and form of the material of thedivider itself (e.g., a curved divider profile) and/or by the dividerpositioning with respect to the conduit structure such as at its fixedend FE. Nevertheless, with or without such a normalized deviationfeature, and in the failure of operation of the flow generator,functional movement of the flexible divider may still occur in responseto patient respiration. For example, patient expiratory flow can stillforce the divider to open to atmosphere allowing expired air to vent toatmosphere so as to prevent rebreathing, even if the flow generator ispowered off.

Operation of the flexible channel divider 2607 may be further consideredin reference to FIGS. 28, 29 and 30 which illustrate inspiration, startof expiration and expiration respectively. As shown in FIG. 28, aninspiratory flow IF across the divider and the lip end LE of the dividerapplies a pressure force (shown as black arrow) against the divider tokeep the divider in a position covering the venting portion 2611 and, ifpresent, overcoming the previously mentioned deviation. Thus, theinspiratory flow IF would move through the first channel CA and thesecond channel CB of the conduit toward the user UE or mask end of theconduit. As illustrated in FIG. 29, at the beginning of expiration, aninitial expiratory flow EF applies a pressure force (shown as blackarrows) at the lip end LE of the divider so as to begin to raise thedivider away from the wall of the conduit 2609. As illustrated in FIG.30, as the expiration flow EF continues, having shifted the lip end LE,the expiratory flow plies a force to the remainder of the deformableportion of the divider that moves the divider away from the ventingportion side of the conduit toward a position on the opposite supportside of the conduit. This movement allows the expiratory flow EF to ventthrough the apertures of the venting portion 2611. It also blocks flowthrough the conduit from the air or gas supply end 2609ASE to the userend 2609UE when the divider seals with a portion of the conduit such asthe divider shelf 2609S. The raised ridges of the divider support 2615help to prevent the flexible divider from curling or overextendingwithin the conduit during expiration, which could undesirably result injamming the flexible divider within the conduit so as to prevent itsreturn to cover the venting portion during inspiration.

The movement of the divider during expiration also dynamically separatesthe channel of the conduit so that the divider has an inspiratory sideIS and an expiratory side ES. Thus, when the flexible divider is formedof a temperature conducting and/or humidity conducting material, thedivider may serve as an exchanger as previously described. Moreover, theassembly may serve as an anti-asphyxia valve when connected to arespiratory treatment apparatus. In the event of a blocked conduit onthe air or gas supply end 2609ASE, a patient's inspiration will deflectthe divider from the venting portion 2611 to allow air intake throughthe venting portion.

A further alternative embodiment of such an assembly is illustrated inFIG. 31. The conduit and divider embodiment of FIG. 31 includes astructure and operates similar to the embodiment of FIGS. 28, 29 and 30.However, this embodiment also includes a continuous vent 3131. Thecontinuous vent will permit a continuous vent flow CVF from a supplysource, such as a flow generator, during expiration as illustrated inFIG. 31, as well as during inspiration (not shown). In this regard,movement of the divider does not block the continuous vent 3131. Duringexpiration, when the divider is moved to its position adjacent to theribs or ridges of the divider support 2615. A continuous vent flow CVFfrom the air or gas supply end 2609ASE will flow around or between theribs of the divider support to pass through one or more apertures of thecontinuous vent 3131.

In the example of FIG. 33, the conduit 2609 employs a bend 3333 in thechannel, such as one formed by the wall of the conduit. The flexibleregion FR of the channel divider 2607 may be positioned proximate to thebend 3333 such that it may extend over the bend. The flexible region FRmay be preloaded or otherwise chosen to have a particular springconstant. The spring constant may serve to bias the channel divider 2607to a particular respiratory event. For example, the spring constant maybe chosen to bias the divider to an expiratory position such that theventing portion 2611 remains normally open, such as in the absence orinsufficient flow or pressurized air directed from the air or gas supplyend 2609ASE. In such a case, the pressure and/or flow required to openthe venting portion (e.g., moving the divider away from the ventingportion) such as the pressure or flow of patient expiration may bereduced when there is a flow from the gas supply end 2609ASE of theconduit. The bend, and the positioning of the divider extending acrossthe bend, may also permit operation of the divider so as to takeadvantage of directional flow (e.g., expiratory flow and the turbulencecreated thereby in relation to the structure of the bend) as well aspressure. Such a divider may have a faster operation, with respect tovalves operating just in response to pressure or just in response toflow, and may permit it to remain open longer with less flow and lowpressure. Moreover, by extending the divider out from the bend (e.g.,the lip end LE), exposing a larger portion of the divider to the flow ofthe channel of the conduit such as when compared to the similar butsmaller extension (e.g., the lip end LE) of the divider in FIG. 26, thelarger extension can provide a divider with more responsiveness tochannel flow (e.g., expiratory flow).

The example vents of FIGS. 26 to 32, as well as others of theapplication, may be suitable for implementation with ventilators, suchas a ventilator that provides volume controlled ventilation (e.g.,pressure support to meet a target measure of ventilation like a minuteventilation or tidal volume etc.). The vent size may be fixed and can beimplemented to provide a positive end expiratory pressure (PEEP)component of therapy. For example, as the flow generator generatespressure against the side of the divider proximate to the gas supply end2609ASE of the conduit, the reaction of the divider thereto andconsequent pressure force required to overcome the divider to vent onthe user side of the divider, can serve to provide the PEEP therapycomponent.

In some cases, the divider and channel may be configured to providedifferent flow activation contact areas on the two sides of the divider(e.g., the side exposed to direct flow from the gas supply end 2609ASEof the conduit when compared to side exposed to direct flow from theuser end 2609UE of the conduit. An example of such a feature isillustrated in the conduit of FIGS. 34 and 25. In this example, the areaof the side exposed to or activated by patient exhalation flow (shown atarrow Y) has a greater area that the area exposed to or activated byflow of the gas supply end (shown at arrow X) (i.e., X<Y). As aconsequence, and based on the chosen areas, a flow generator may providehigher flows/pressures for patient treatment on the gas supply sidewhile still permitting a response by the divider to the smallerpressure/flows of patient expiration at the user side so as to ensureopening of the divider to vent flow through the venting portion 2611during expiration. Optionally, the vent of FIG. 34 may also employ acontinuous vent 3131, which may optionally be pre-set to have differentvent flows.

In some examples, the surface of the divider, although optionally atleast in part flexible, may have a planar shape. However, in someexamples the divider may conform to non-planar surface shapes and mayoptionally be rigid or deform therefrom under chosen flow and pressurecharacteristics. Such shapes may promote different flexibility and/ormovement characteristics of the divider as desired. For example, asillustrated in FIG. 36, the surface of the gas supply end 2609ASE of thedivider 2607 may have a concave surface. Optionally, a convex surfacemay be formed at its opposite side, facing the user end 2609UE of theconduit 2609. In some examples, such surfaces may be reversed. Forexample, the surface of the gas supply end 2609ASE of the divider 2607may have a convex surface and a concave surface may be formed at itsopposite side, facing the user end 2609UE of the conduit 2609. In somecases, the divider may be formed with a rigid or flexible bend, curve orlift LFT at its lip end extending into a channel of the conduit, such asthe example illustrated in FIG. 37. Such a divider will normallymaintain the shape of the lift. Such a lift may promote or ensureexposure of the divider to certain flows of the conduit, such as anexpiratory flow from the user end 2609UE.

In the example of FIG. 38, the divider 2607 is coupled to a pivot 3855.The movement of the divider 2607, such as in response to patientexpiration, may further drive a vent cover 3857, which may be configuredexternally to the conduit, of a secondary vent 3859. Such a linkedmovement of the vent cover 3857 may open the secondary vent 3859 torelease pressure/flow of the conduit so as to permit escape of air orgas generated at the gas supply end 2609ASE of the conduit. Thus, whenthe divider is in its expiratory position such that the venting portion2611 is generally open during patient expiration, the secondary vent mayopen contemporaneously. This case is illustrated in FIG. 38. Conversely,when patient expiration ceases (or inspiration begins), the divider willmove to cover the venting portion 2611 such as a result of flowgenerated at the gas supply end 2609ASE of the conduit. When thisoccurs, the linked vent cover 3857 will similarly close against thesecondary vent 3859 such that the flow of the conduit from the gassupply end will proceed to the user end. This case is illustrated inFIG. 39.

As also illustrated in FIGS. 38 and 39, the divider 2607 may beimplemented with one or more divider protuberant(s) 3861. Each dividerprotuberant 3861 may be configured to plug or seal one or more aperturesof the venting portion 2611. Thus, when the divider moves toward theventing portions, apertures of the venting portion may be filled orsealed by one or more protuberants of the divider as shown in FIG. 39.Optionally, the vent cover may have similar protuberant structures forsealing the secondary vent as illustrated in FIG. 39. The shape of theapertures filled by each protuberant may typically have a shape thatcorresponds to the shape of the protuberant. For example, in the case ofa conic protuberant, the aperture may have a conic inner cavity.

FIGS. 40 and 41 illustrate implementation of a divider 2607 formed in acylindrical arrangement such as with a duckbill opening 2607OP. A frontview of the duckbill opening 2607OP end of the divider is furtherillustrated in the callout bubble CC. The divider operates by openingand closing at the duckbill opening 2607OP to either permit or precludea flow of gas from the gas supply end 2609ASE of the conduit to the userend 2609UE of the conduit through the divider. A greater breathable gaspressure or flow from the gas supply end 2609ASE compared to the userend 2609UE, such as from a flow generator of a respiratory treatmentapparatus during patient inspiration, forces the duckbill opening to anopen position. When the duckbill opening 2607OP is open, as illustratedpartially in the callout bubble CC of FIG. 40 and fully in FIG. 41, flowproceeds in a direction of flow arrows F through a cylindrical portion2607CP inside of the divider. In its fully open position, portions ofthe cylindrical surface of the divider move to cover apertures of theventing portions 2611 of the conduit. The apertures of the ventingportions may reside along the internal peripheral surface of the conduit2609. Such a divider may, have a normally closed position, for examplewhen formed of a resilient material, such that a first portion 2607FPand second portion 2607SP move together to fold the divider and closethe duckbill opening 2607OP in the absence of a greater pressure forceat the gas supply end 2609ASE of the conduit. In this folded position,the venting portion 2611 is uncovered by the divider. As a result, airmay escape through the venting portion 2611 such as during patientexpiration when the pressure at the user end 2609UE is greater than thepressure at the gas supply end 2609ASE.

In the example conduit of FIGS. 42 and 43, a divider is implemented witha discrete chamber 4299 with an expiratory venting chamber portion 2611Cthat leads to the venting portion 2611 and a release chamber portion4261 that leads to a pressure equalization aperture 4243. The dividerseparates the expiratory venting chamber portion 2611C from the releasechamber portion 4261. In the example, the divider's fixed end FE residesin the discrete chamber such as at a pivot 4255 and the lip end mayextend out of the chamber and into, and across, a channel of theconduit. Motion of the divider selectively opens and closes the chamberto either the expiratory venting chamber portion 2611C or the releasechamber portion 4261 from the conduit. This divider movement alsoselective opens and closes the flow channel of the conduit between thegas supply end 2609ASE and the user end 2609UE. For example, duringpatient expiration, as illustrated in FIG. 42, the divider pivots toopen access to the expiratory venting chamber portion 2611C from theuser end of the conduit so that expiratory flow may vent into thediscrete chamber from the flow channel FLC of the conduit 2609. Once inthe expiratory venting chamber portion 2611C, the flow F can pass outthe apertures of the venting portion 2611. During patient inspiration,as illustrated in FIG. 43, the divider 2607 moves to close access to theexpiratory venting chamber portion 2611C and thereby open flow channelaccess to the release chamber portion 4261. This movement alsocontemporaneously opens access, of the flow channel of the conduit fromthe gas supply end 2609ASE of the conduit to the user end 2609UE of theconduit. The flow of the conduit from the gas supply end then mayproceed along the divider around the lip end LE toward the user end. Thepressure equalization aperture 4243 may be a fine hole or holespermitting the release chamber portion 4261 to equalize with atmosphere.Such a pressure equalization can promote return of the divider to itsexpiratory position (shown in FIG. 42) during patient expiration whenthe pressure in the release chamber portion 4261 is lower than thepressure on the opposing side of the divider due to patient expiration.However, the pressure equalization aperture 4243 does not significantlyreduce the pressure or flow of the channel between the gas supply end2609ASE and the user end 2609UE.

In the example illustrated in FIGS. 44 and 45, which is similar indesign and operation to the examples of FIGS. 26 to 31, the flexiblechannel divider 2607 is configured within a conduit formed as a couplerwith coupler ends CE. The coupler may be connected with other conduitsor patient interface, such as a mask component. In this example, theconduit is equipped with inspiratory and expiratory divider supports2615 which prevent excessive travel of the divider or otherwise limitthe travel of the divider to desired locations as the divider movesbetween the opposing supports. The inspiratory divider supports 2615-Iare located on an opposing side of the conduit from the side with theexpiratory divider supports 2615-E. As shown in FIG. 44, the inspiratorydivider supports, such as one or more ribs, support the divider duringinspiration. Similarly, as shown in FIG. 45, the expiratory dividersupports, such as one or more parallel ribs, support the divider duringexpiration. Passages between the ribs of the divider supports (not shownin FIGS. 44 and 45) permit gas flow to contact a greater area of asupported side SS of the channel divider when supported by the dividersupports so as to permit more readily lifting of the divider away fromthe supports. As also illustrated in FIGS. 44 and 45, the conduitsdescribed herein may also be equipped with an expiratory diffuser 4444at the venting portion 2611 such as a foam material diffuser. Theexpiratory diffuser may help to reduce noise associated with the ventingof expiratory gas at the venting portion 2611. In some cases, theexpiratory diffuser provides a low turbulence and low noise escapepathway. It may also increase impedance of the expiratory path. Such anincrease may serve to increase the pressure on the flexible dividerduring expiration and improve the divider's response.

In some cases, the conduits described herein, such as the conduitsemploying a channel divider may be equipped with a bypass channel 4690.The bypass channel 4690 may help to permit a small flow of expiratorygas to bypass the divider. For example, the bypass channel may connectthe channel of the conduit on either side of the divider and may runthrough a wall of the conduit in the sense of being integrated with thewall of the conduit. However, in some cases, small connection ports (notshown) each connecting an interior with the exterior of the conduit wallon both sides of the divider may be coupled together with an additionalconduit. Such a bypass of gas may then be sensed by a sensor such aswhen a sensor is positioned up stream of the channel divider. Such asensor may be more proximate to or within a flow generator to which theconduit is coupled. Such an upstream sensor may then be employed fordetecting the patient's respiratory cycle (e.g., inspiration andexpiration) and/or pressure in the mask during inspiration andexpiration. Alternatively, sensors may be positioned on the patient sideof the channel divider such as for detecting a user's respiratory cyclefrom flow and/or pressure sensors. Example methods for measuring suchpressure and flow characteristics are described in more detail herein.Generally, with such a configuration, the bypass flow path can assistwith estimating and monitoring expiratory mask pressure and patient floweven when the channel divider is diverting expiratory flow to theventing portion. In this regard, during inspiration the bypass path mayhave a negligible effect because it can be a very high impedance pathcompared to the main channel. However, during expiration, the bypasspath allows a small amount of flow back towards flow generatorsensor(s). This amount of flow can be small enough to be insignificantto the patient's therapy, but can still enable monitoring of patientexpiratory parameters from sensor(s) in the flow generator, such aspressure and/or flow.

As previously described herein, the example channel dividers mayoptionally be configured so as to serve as an exchanger. However, theefficiency of any exchange between the inspiratory and expiratory gassides of the divider may be increased or implemented by additionalexchanger materials, such as upstream and/or downstream of the divider.For example, a filter-like material or foam may be employed in serieswith the divider of the examples discussed herein. One such example isillustrated in FIG. 47. Such a heat moisture exchange material 4747 isdisposed in a common channel of the conduit through which bothinspiratory and expiratory gas pass (a bi-directional channel), such asdownstream of the divider and more proximate to the patient interfaceend. Within such a material, both inspiratory and expiratory gases willpass such that there is no distinct inspiratory and expiratory side.Suitable heat moisture exchange materials may includepolytetrafluoroethylene (PTFE). The material may be made of a spongymaterial, a corrugated paper, a bundle of hollow fibres and/or multiplelayers of PTFE, any of which may be further treated with a hygroscopicmaterial.

In the example of FIG. 48, an additional exchanger 106 is added upstreamof the divider in the conduit, more proximate to a flow generator. Tofurther facilitate the distinct inspiratory channel 102 and expiratorychannel 104, the conduit 2609 may include an expiratory extensionchamber 4848, into which apertures of the venting portion 2611 ventexpiratory gas. An extension opening 4849 may then permit a release ofthe expiratory gas to atmosphere.

In some cases, the conduit may be implemented with an adjustablecontinuous vent or a patient interface with such a vent to permit apatient to control setting of the level of humidity in the patientinterface. Such a venting feature may typically be downstream of thedivider, closer to the user such that when open the adjustablecontinuous vent will permit venting during expiration and inspiration.The amount of such venting may then be set by a user so as to permit thepatient to choose her own level of temperature and humidity comfort. Themore the patient increases the continuous vent flow (e.g., by enlargingits opening(s)) it can decrease the humidity affect associated with theaction of the divider. For example, some patients may not like feelingtoo much humidity in the patient interface. In one such example, a dialor sliding adjustment may be implemented that allows the patient to setthe level of continuous venting. Such a dial or sliding adjustment mayincrease or decrease the openings of the continuous vent. In anotherexample, vent apertures of the continuous vent may include vent plugsthat may be manually removed (or added) as desired to adjust the levelof additional venting via the unplugged apertures of the continuousvent.

Venting Characteristics

In some systems that implement components described herein, it may bedesirable to control a therapy pressure. For example, in someimplementations, approximate control of the therapy pressure may beachieved by a controller that runs a blower at a constant angular speed.In other implementations control of the therapy pressure may be achievedby a controller that implements a pressure control loop and acharacterisation of the gas delivery system.

Consider the simplified electric circuit analogy of such a system as inFIG. 49 showing typical components of the system as impedance components(Z) (supply conduits, vent and patient airways) and capacitivecomponents (C) (e.g., patient airways) and voltage components (V) (e.g.,flow generator “FG” and patient respiratory muscles “mus”). Pressure andflow characteristics of such components may be considered with referenceto FIGS. 49A, 49B and 49C. FIG. 49A illustrates example supply conduitresistance for various supply tube sizes (i.e., 10 mm supply tube and 19mm supply tube). For example, the smaller supply tube experiencesgreater pressure loss at flows levels compared to larger supply tube atthe same flow level. FIG. 49B shows pressure and flow characteristicswith reference to a fan curve of a flow generator formed by a motorizedimpeller. Characteristics of a continuous-type orifice vent areillustrated in the graph of FIG. 49C showing a relationship betweenpressure and flow. In such a system, the purpose of continuous ventingis to allow for the removal of the carbon dioxide from the system, toprevent it from being inspired. But as seen from FIG. 50, the volume ofair vented will greatly exceed the volume of expired air, which is thesource of the carbon dioxide. FIG. 50 shows the vented air volume withreference to signals corresponding to flow generator-flow (FG-flow) andpatient flow (PT-flow). As illustrated, the volume of vented air duringexpiration corresponds with carbon dioxide (CO₂).

In some of the examples of the present technology, venting may beminimized during inspiration and all or substantially all of the expiredair is vented during expiration. Moreover, the flow generator does notneed to produce any more flow than necessary such as when the flow pathfrom the flow generator to the patient is closed during expiration. Andimportantly, the flow the patient is exposed to is not significantlygreater than patient flow. This can have positive implications forpatient perception of the therapy, and its effect on drying the patientairways. Flow (Q) and pressure (P) may be considered by the followingequations:

During inspiration:Q _(FG) =Q _(Patient) +Q _(LEAK)

Or if there is no leakQ _(FG) =Q _(Patient)

During ExpirationQ _(FG)=0P _(FG) =P _(end of supply tube) (Approximately=P _(therapy), for lowpatient flows)

Where Q_(FG) is flow generator flow; Q_(Patient) is patient flow;Q_(LEAK) is leak flow; P_(FG) is the pressure at the flow generator andP_(end of supply tube) is the pressure at the end of the supply conduit.

This is further illustrated in the graph of FIG. 53, which may becompared with the graph of FIG. 50. In FIG. 53, the venting of airoccurs during expiration and the flow generator flow corresponds withpatient inspiratory flow.

Having low, or no venting on inspiration may provide other advantagessuch as low acoustic noise, as well as low signal noise in the pressureand flow signal, because at lower velocity there is less turbulence inthe air. The low noise signals may make detection of other phenomenamore accurate, such as detection of cardiogenic flow. There may also beadvantages in the use of forced oscillation techniques, such as fordetecting open and closed airways, and the measurement of respiratorymechanics, such as airway resistance and compliance.

FIGS. 57 and 58 further illustrate simulated performance of an exampledevice having a channel divider such as the embodiment of FIG. 26, 32 or44. The graph of FIG. 56 illustrates performance of a traditionalcontinuous vented mask. The graphs of FIGS. 56, 57 and 58 show thepatient flow (PT-flow), the flow generator flow (FG-flow) and thetherapy pressure in a mask, that is, delivered pressure to patient(MSK-p) on a common time axis. The pressure is in a cmH₂O scale up thegraph and the flow is a L/sec scale up the graph. FIG. 57 illustrates atest of the channel divider device showing that most of thepressure/flow provided by the flow generator is provided to the patientwith very little pressure/flow loss. There are also low pressure swingsbetween the inspiration and expiration phases. The graph of FIG. 56shows the same test with a standard continuous-type vented mask withoutthe divider flap. The graph shows that there is a much largerpressure/flow loss between the pressure/flow provided by the flowgenerator and the pressure provided to the patient. There are also muchlarger pressure swings. Lastly, this graph of FIG. 58 illustrates thatthe level of flow stays generally constant such that it is unaffected bypressure during a ramping of treatment pressure to the patientcontrolled by the flow generator.

Expiratory Characteristic Sensing

In the case of implementation of a bypass channel as discussed withreference to FIG. 46, a controller, such as one with a processor coupledwith a sensor, may be configured to estimate patient flow or maskpressure. Example functions for such estimates are described herein. Asillustrated in the graph of FIG. 55, a flow sensor may sense flow duringinspiration normally but during expiration only a small flow quantity(i.e., less than a typical expiration quantity) through the small bypasschannel.

For such a bypass flow path, the relationship between pressure andturbulent flow may be modelled as a second order polynomial.P _(therapy) =K ₁ *Q _(FG) ² +K ₂ *Q _(FG) +P_(end of supply tube)  (Eq1)Where:

-   -   P_(therapy)−P_(end of supply tube) is the pressure difference        across the bypass flow path;    -   Q_(FG) is the flow through the bypass flow path, which is equal        to the bypass flow during patient expiration.    -   K₁ and K₂ are constants depending on the physical properties of        the bypass path, such as geometry and surface finish.    -   Wherein P_(therapy) is the therapy pressure such as the pressure        in the mask; and P_(end of supply tube) is the pressure at the        end of the supply tube.

Thereby, during expiration, the mask or therapy pressure may beestimated by the controller from this relationship and the pressure andflow in the flow generator. During inspiration, a traditional sensing ofpressure may be implemented by the controller. In this sense, thecontroller may be configured with one methodology for determiningpressure at the mask during inspiration and a different methodology fordetermining pressure in the mask during expiration.

Furthermore, the relationship between the patient expiratory flow out ofthe expiratory vent and the therapy pressure may be modelled as secondorder polynomial for a particular end of tube pressure:P _(therapy) =K ₃ ·Q ² +K ₄ ·Q+P _(end of supply tube)  (EQ2)

Where K₃ and K₄ are constant for a particular range of end of tubepressures and patient flow.

To assist with providing either a comfortable or controllable therapy itmay be desirable to arrange the system such that for patient expirationa large range of expiratory flows relates to a relatively small range indifferential pressures (between therapy and atmosphere) for a particularend of supply tube pressure. This requires relatively small values of K₃and K₄. This can be achieved by having a large enough aperture and bycontrolling the dynamic pressure the flow exerts on the flexibledivider.

Equation (EQ2) may also take different forms, such as if K₃ and K₄ aremade very small the equation may be approximated as:P _(therapy) =P _(end of supply tube)  (EQ3)

The relationship may be better modelled as a function (f) other than apolynomial, or a higher order polynomial, for example, a non-monotonicrelationship such that at lower patient flow rate a higher component ofstatic therapy pressure is applied to straining the flexible divider,and at higher flow rates the dynamic component of the gas pressure, andthe component of the pressure associated with accelerating the gas/fluidby changing its direction may form a larger proportion of the pressurerequired to strain the divider such that the static pressure componentshould be less. Practically, this allows less mask pressure at higherpatient flows for particular ranges of therapy pressures and patientflows.P _(therapy) =f(P _(end of supply tube,) Q _(patient))  (EQ4)

Similarly, the pressure loss with flow relationship in the connectingtubes may be characterised asP _(end of supply tube) =K ₅ *Q2+K ₆ *Q+P _(FG)  (EQ5)Thus, from measurements of the pressure and flow in the flow generatorit is possible to estimate the pressure at the end of the supply tube(e.g., with pressure drop characteristics of the supply tube), and thenusing any of the equations above it is possible for a processor toderive estimates for the therapy pressure and patient flow, such asduring expiration. For example, the estimated patient flow isillustrated in the graph of FIG. 55. In such a case, a controller orprocessor may be programmed with data and instructions for implementingthe functions or equations. Thus, a flow generator apparatus may includeintegrated chips, a memory and/or other control instruction, data orinformation storage medium. Programmed instructions encompassing suchmethodologies may be coded on integrated chips in the memory of thedevice or apparatus to form an application specific integrated chip(ASIC). Such instructions may also or alternatively be loaded assoftware or firmware using an appropriate data storage medium.

With an estimate of patient flow and therapy pressure (as described) itis possible to control therapy pressure, and to perform all of thealgorithms that utilize or analyse such information, such as CPAP,autoset CPAP, bi-level therapy, apnoea/hypopnoea detection, measurementof patient compliance, estimate of tidal volume, targeting a tidalvolume with pressure support, expiratory pressure relief, detection ofrespiratory rate, etc.

While such dividers are generally capable of passive or pneumaticoperation as discussed herein based on changes in flow and pressureprimarily attributable to patient respiration and/or flow generatorpressure adjustments, other controlled operation configurations may beimplemented. For example, the dividers may be actively controlled bymotorized components, electro-magnetic control components etc. Forexample, the divider may be formed with plastic or metal materials andmay be magnetic so as to be selectively responsive to one or morecontrolled magnetic fields, such as from an electro-magnet or fieldcoils controlled by a controller of the apparatus with which the conduitis utilized (e.g., a respiratory treatment apparatus controller). Insome cases, the divider may be configured to change shape (e.g., shrinkand grow) based on a selective application of electrical potential so asto control the divider to open and close a venting portion. The conduitwith the dividers described herein may be implemented to be part of orclosely implemented with a patient interface (e.g., a respiratory mask).However, the conduit may also be implemented farther away such as beingmore proximate to, or even in, the gas supply components or flowgenerator rather than to the mask. In some cases, a leak vent may beadded to the conduit to provide a continuous leak (e.g., a 5 ml flowleak) such that the divider does not open and close the leak vent.

In this specification, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise”, “comprised” and “comprises” where they appear.

While particular embodiments of this technology have been described, itwill be evident to, those skilled in the art that the present technologymay be embodied in other specific forms without departing from theessential characteristics thereof. The present embodiments and examplesare therefore to be considered in all respects as illustrative and notrestrictive. Thus, any one or more of the features of any exampledescribed herein may be applied to any of the other examples describedherein. It will further be understood that any reference herein tosubject matter known in the field does not, unless the contraryindication appears, constitute an admission that such subject matter iscommonly known by those skilled in the art to which the presenttechnology relates.

The invention claimed is:
 1. A conduit for a breathable gas for apatient interface that delivers a respiratory treatment generated by arespiratory treatment apparatus, the conduit comprising: a conduithaving a first channel and a second channel, the first channelconfigured to conduct an inspiratory gas and the second channelconfigured to conduct an expiratory gas, and a flexible channel divideralong the first channel and the second channel to dynamically create thefirst channel and the second channel in response to an inspiratory flowand an expiratory flow, wherein the divider is configured to create aninspiratory channel between a first side of the conduit and a first sideof the divider and an expiratory channel between the opposing side ofthe conduit and the opposing side of the divider when the dividertraverses between the opposing sides of the conduit.
 2. The conduit ofclaim 1 wherein the flexible channel divider comprises an exchanger totransfer a component of a gas of the second channel to the firstchannel.
 3. The conduit of claim 2 wherein the component is temperature.4. The conduit of claim 3 wherein the component is humidity.
 5. Theconduit of claim 1 wherein the flexible channel divider has a fixed end.6. The conduit of claim 1 wherein the flexible channel divider has a lipend.
 7. The conduit of claim 1 further comprising a venting portion,wherein the flexible channel divider is configured to move toselectively block and open an aperture of the venting portion of theconduit.
 8. The conduit of claim 7 wherein the venting portion comprisesa set of oblique apertures.
 9. The conduit of claim 7 wherein theventing portion comprises a set of apertures configured at an acuteangle with respect to an expiratory flew path of the second channel. 10.The conduit of claim 7 wherein the flexible channel divider comprisesone or more protuberants configured to seal at least a part of theventing portion.
 11. The conduit of claim 7 further comprising asecondary vent and a vent cover, wherein the flexible channel divider islinked to the vent cover for selectively sealing the secondary vent. 12.The conduit of claim 1 wherein the conduit further comprises a ribbeddivider support.
 13. The conduit of claim 12 wherein the conduit furthercomprises a divider seat configured for sealing with a peripheral edgeof the divider.
 14. The conduit of claim 1 wherein the conduit furthercomprises a continuous vent aperture.
 15. The conduit of claim 1 furthercomprising a conduit bend, wherein the flexible channel divider extendsacross the conduit bend.
 16. The conduit of claim 1 wherein a length ofthe flexible channel divider comprises a length greater than one and onequarter times width of the conduit.
 17. The conduit of claim 1 whereinthe flexible channel divider is configured in the conduit to provide theflexible channel divider with an expiratory activation side an gassupply activation side, wherein the expiratory activation side has asurface area exceeding a surface area of the gas supply activation side.18. The conduit of claim 1 wherein the flexible channel dividercomprises a lift at a lip end of the divider, the lift extending into achannel of the conduit.
 19. The conduit of claim 1 wherein the flexiblechannel divider comprises a non-planar surface.
 20. The conduit of claim19 wherein the non-planar surface is a convex surface.
 21. The conduitof claim 1 wherein the conduit comprises a bypass channel configured topermit a sensing of a gas characteristic to bypass the flexible channeldivider.
 22. The conduit of claim 21 wherein the conduit is coupled ingas communication with a sensor, the sensor configured to sense a gascharacteristic attributable to the bypass channel, the sensor coupledwith a processor, wherein the processor is configured to estimate a gascharacteristic of an opposing side of the flexible channel divider fromthe sensed characteristic.
 23. The conduit of claim 22 wherein theestimated characteristic comprises patient expiratory flow.
 24. Theconduit of claim 22 wherein the estimated characteristic comprisestherapy pressure at a patient interface.
 25. The conduit of claim 1further comprising an exchanger in series with the flexible channeldivider.
 26. The conduit of claim 1 further comprising a heat moistureexchange material in a bi-directional flow channel in series with theflexible channel divider.
 27. The conduit of any one of claim 1 furthercomprising a set of divider supports extending from a conduit surfaceand positioned to support the divider during an inspiratory flow. 28.The conduit of claim 1 further comprising a set of divider supportsextending from a conduit surface and positioned to support the dividerduring an expiratory flow.
 29. The conduit of claim 27 wherein the setof divider supports comprise parallel ribs longitudinally arranged alongthe flow path of the conduit.
 30. The conduit of claim 1 wherein theflexibility of the divider permits the expiratory channel to vary inopening size to be more open with higher expiratory patient pressures.